We're dividing 81539866 by 640 
The aim is to understand the frequency of 640 in 81539866.

Going ahead to step 1:
When dividing 8 by 640, we get 0 with a remainder of 8.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we take 0 away from 8, we end up with 8.
Take the next digit (1) from the dividend and append it to 8, then repeat: 81 / 640

Advancing to step 2:
640 goes into 81 0 times with a remainder of 81.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we take 0 away from 81, we end up with 81.
Grab the next digit (5) from the dividend, add it to 81, then carry on: 815 / 640

Moving on to step 3:
When dividing 815 by 640, we get 1 with a remainder of 175.
Put 1 as the next digit of the answer. 
Result so far: 1.0
The remainder is 175 after subtracting 640 from 815.
Take the next digit (3) from the dividend and append it to 175, then repeat: 1753 / 640

Going ahead to step 4:
640 goes into 1753 2 times with a remainder of 473.
Write down 2 as next digit of the result. 
Result so far: 12.0
Deduct 1280 from 1753 and we're left with 473.
Bring next digit (9) of the dividend behind the 473 and repeat the process: 4739 / 640

On to step 5:
640 can be fit into 4739 7 times, resulting in a remainder of 259.
Use 7 as the next digit of our solution. 
Result so far: 127.0
The remainder is 259 after subtracting 4480 from 4739.
Include the next digit (8) from the dividend after 259, then repeat: 2598 / 640

On to step 6:
2598 divided by 640 is 4 with a remainder of 38.
Put 4 as the next digit of the answer. 
Result so far: 1274.0
If we subtract 2560 from 2598, we get 38.
Append the next digit (6) from the dividend to 38 and continue with: 386 / 640

Moving on to step 7:
386 divided by 640 is 0 with a remainder of 386.
The number 0 becomes the next digit in our result. 
Result so far: 12740.0
If we take 0 away from 386, we end up with 386.
Include the next digit (6) from the dividend after 386, then repeat: 3866 / 640

Going ahead to step 8:
When dividing 3866 by 640, we get 6 with a remainder of 26.
Write down 6 as next digit of the result. 
Result so far: 127406.0
Subtracting 3840 from 3866 leaves us with 26.
Since there are no more digits in the dividend, we add a zero to the remainder making it 260, and continue the process.

Moving on to step 9:
The number 640 fits into 260 0 times, leaving a remainder of 260.
The next digit of our result is 0. 
Result so far: 127406.0
Deduct 0 from 260 and we're left with 260.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2600, and continue the process.

Going ahead to step 10:
When dividing 2600 by 640, we get 4 with a remainder of 40.
The next digit of our result is 4. 
Result so far: 127406.04
If we subtract 2560 from 2600, we get 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

On to step 11:
640 can be fit into 400 0 times, resulting in a remainder of 400.
The number 0 becomes the next digit in our result. 
Result so far: 127406.04
If we take 0 away from 400, we end up with 400.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4000, and continue the process.

Advancing to step 12:
640 goes into 4000 6 times with a remainder of 160.
Record the quotient 6 as the next digit in the result. 
Result so far: 127406.0406
Deduct 3840 from 4000 and we're left with 160.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1600, and continue the process.

On to step 13:
1600 divided by 640 is 2 with a remainder of 320.
The next digit of our result is 2. 
Result so far: 127406.04062
The remainder is 320 after subtracting 1280 from 1600.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3200, and continue the process.

Let's proceed to step 14:
The number 640 fits into 3200 5 times, leaving a remainder of 0.
Record the quotient 5 as the next digit in the result. 
Result so far: 127406.040625
The remainder is 0 after subtracting 3200 from 3200.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Advancing to step 15:
When dividing 0 by 640, we get 0 with a remainder of 0.
Write down 0 as next digit of the result. 
Result so far: 127406.040625
The remainder is 0 after subtracting 0 from 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Step 16:
If we divide 0 by 640, we get 0 and a remainder of 0.
Record the quotient 0 as the next digit in the result. 
Result so far: 127406.040625
The remainder is 0 after subtracting 0 from 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

After the division, we end up with 127406.040625 and a remainder of 0.0.